ZnO Multipods Research Articles

Microwave-assisted rapid synthesis of ZnO multipod-BiOBr heterojunction on recycled PET plastic waste for photocatalytic degradation of oily wastewater

Heterojunctions based on ZnO multipod and BiOBr were developed on the floating recycled polyethylene terephthalate (PET) and they were used to investigate the photocatalytic degradation of hexane in water emulsion. Characterizations of the synthesized ZnO-BiOBr-PET photocatalysts was performed using XRD, FESEM, EDX, BET/BJH, FTIR, UV-Vis DRS, PL, WCA, and CV analyses. The FESEM results demonstrated that ZnO multipods have been synthesized during the very short time of microwave heating that effectively hosted the highly dispersed BiOBr nanoplates, particularly in the 15 %ZnO-5 %BiOBr-80 %PET sample. The BET/BJH analysis revealed the low surface areas for the synthesized samples, however, the sample with the highest ZnO multipod loading (15 %ZnO-5 %BiOBr-80 %PET) exhibited slightly enhanced surface area due to the highly dispersed BiOBr over the ZnO multipods. The fabricated samples displayed hydrophobicity and liquid marble like behaviour due to the presence of PET, while the variations in the percentages of ZnO and BiOBr strongly influenced the water contact angle. The formation of heterojunction between ZnO multipod and BiOBr was confirmed which lead to a shift in the visible light region, increased the light harvesting, and also reduced the charge carrier recombination in the composite sample of 15 %ZnO-5 %BiOBr-80 %PET. The ZnO-BiOBr-PET photocatalysts were tested for the photocatalytic degradation of hexane in a water emulsion and results indicated that 15 %ZnO-5 %BiOBr-80 %PET could degrade 92.1 % of initial hexane, retaining its performance over four successive runs with only an 11.7 % decrease in activity. Scavenger tests revealed that, in addition to hydroxyl radicals, superoxide also played a significant role in the photocatalytic degradation of hexane. This obervations indicate the efficient capturing and utilizing of O2 by this LMP even in non-oxygenated conditions.

Subppb level monitoring and UV degradation of triclosan pollutants using ZnO multipod and Ag nanocomposites

A unique nanomaterial platform was developed for trace detection and efficient degradation of triclosan (TCS). A facile spectroscopic technique for surface-enhanced Raman scattering (SERS)-supported identification and ultraviolet (UV) degradation of TCS using a SERS template based on silver spherical nanoparticle (AgNP)-modified ZnO multipods (ZnO@Ag) is reported. Core-shell composite materials of ZnO multipods with a dimension of around 3 μm and AgNPs with an average diameter of ∼27 nm was designed not only as a substrate for TCS degradation up to ∼92% upon UV irradiation (λ = 365 mm, 300 μW/cm2) but also as a monitoring platform sensitive to TCS at a detection limit as low as 10−9 M (≈0.3 ppb). Herein, the first investigation into ZnO@Ag bimetallic composites is established for both the SERS-based detection and UV-assisted degradation of environmental TCS pollutants. The calibration curve was estimated to be linear at R2 > 0.97. The validated technology was successfully used to determine the antibacterial agent and TCS in distilled or river water. The advantages of the ZnO@Ag template are highlighted over conventional detection and excellent degradation.

Ultraviolet Luminescence of ZnO Whiskers, Nanowalls, Multipods, and Ceramics as Potential Materials for Fast Scintillators

The presented work is dedicated to the study and comparison of scintillating properties of zinc oxide samples prepared in different morphologies: whiskers, nanowalls, multipods, and ceramics. It was shown that total transmittance, photo- and radioluminescence spectra, and radioluminescence kinetics can vary significantly depending on sample structure and preparation conditions. The highest total transmittance was registered for ZnO ceramics (>50% at 0.5 mm thickness). Differences in the transmittance of whiskers, nanowalls, and multipods can be attributed to their shape and thickness which affects the amount of light refraction and scattering. The study of radioluminescence demonstrated that all samples, except undoped ceramics and air annealed whiskers, have predominantly fast luminescence with a decay time <1 ns. High transmittance of ceramics opens the way for their use in the registration of high energy X-ray and gamma radiation, where a large volume of scintillators is required. In cases, where large scintillator thickness is not a necessity, one may prefer to use other ZnO structures, such as ensembles of whiskers and nanowalls. Studies of near-band-edge luminescence components at low temperatures showed that the structure is quite similar in all samples except Ga doped ceramics.

Facile and ultra-rapid synthesis of multi-pod ZnO nanostructures through thermal heating using the flame of a portable gas torch

ZnO nanostructures with a multi-pod morphology were formed ultra-rapidly in just 15 s using the hot flame of a gas torch in air at atmospheric pressure. Zn powder was used as the starting material. No catalysts were employed. The average diameter and length of the pods were 130 nm and 750 nm, respectively. The multi-pod ZnO nanostructures had a hexagonal wurtzite crystal structure and exhibited a strong ultraviolet emission at 380 nm. The experimental results reveal that the synthesis process employed in the present work is a simple, economical, and ultrafast method to produce multi-pod ZnO nanostructures with high purity and crystallinity.

Hetero-seed meditated method to synthesize ZnO/TiO2 multipod nanostructures with ultra-high yield for dye-sensitized solar cells

ZnO multipod nanostructures are widely used for their unique structures. However, the large-scale synthesis of these materials is a challenge for the practical applications. In this paper, we used a hetero-seed mediated hydrothermal method to synthesize ZnO/TiO2 multipod nanostructures with ultra-high yield. The TiO2 nanoparticles were used as the seeds and nucleated centers for the following ZnO nanorods growth, in which these ZnO nanorods scattered from the TiO2 nanoparticles to form ZnO/TiO2 multipod nanostructures. The diameter and length of these ZnO nanorod branches were controlled by the amount of TiO2 nanoparticles. The yield of pure ZnO/TiO2 multipod nanostructures can reach 20.0 g/L within 20 min heating time. When used as the anodes of dye-sensitized solar cells (DSSCs), a photoelectric conversion efficiency of 3.1% has been achieved when using these ZnO/TiO2 multipod nanostructures as the anodes of DSSC. This is due to the one-dimensional (1D) nanostructures are promising by fastening electron transport to reduce the charge recombination. As a result, this provides a simple method to synthesize ZnO/TiO2 multipod nanocomposites with high yield and low cost, which can be used as the photoanodes for high efficient DSSCs and photocatalysts.

Effect of boundary layer thickness on ammonia gas sensing of Cr2O3-decorated ZnO multipods

New insights into controlling boundary layer thickness are investigated in growth of Cr2O3-decorated ZnO multipods on a tilted silicon substrate. In the first step, ZnO multipods were grown on a tilted silicon surface using a vapor transport method in a quartz tube. Next step, low concentration of Cr2O3 nanoparticles was decorated on the ZnO multipods using a PVD machine. Both arm diameter and density of the Cr2O3-decorated ZnO multipods were found to be strongly dependent on the boundary layer thickness. The sensing properties of the samples measured by half bridge method indicated that decoration of the Cr2O3 nanoparticles on the ZnO multipods significantly enhanced the response to 100 ppm NH3 up to 85, CO2 up to 29 and NO2 up to 27. The response/recovery times were 25 s/48 s at 300 °C. Blue defect emission appeared in room temperature photoluminescence spectra of the sample grown in a thin boundary layer thickness.

The effect of sodium polyanethol sulfonate on the precipitation of zinc oxide

A very strong effect of sodium polyanethol sulfonate (SPAS) on the formation and properties of ZnO particles was noticed. ZnO particles were prepared by hydrothermal treatment of zinc acetylacetonate in an aqueous medium in the absence or presence of SPAS. All prepared samples were characterized with the XRD, FE-SEM, FT-IR and UV/Vis techniques. Two different mechanisms are proposed for the formation of hollow ZnO particles. In the absence of SPAS ZnO rods were precipitated in the micron range, whereas in the presence of SPAS hexagonal ZnO particles with holes were obtained. The inner dissolution of hexagonal ZnO particles was promoted by the chemically active Zn-(0001) plane attacked by polyanethol sulfonate groups. By adding NH4OH to the precipitation system in the absence of SPAS, multipod (star-like) ZnO particles were formed. When SPAS was added to this precipitation system twin ZnO particles were formed and they were hollow inside. In this case the formation of ZnO particles was explained by the self-assembling mechanism supported by the presence of SPAS. Hexagonal and elongated ZnO particles were laterally arrayed. In this process the specific adsorption of polyanethol sulfonate groups played an important role. Determined were the band gap values of ZnO samples that are typical of “wet” precipitated ZnO.

Growth of Multipod ZnO Architectures Made by Accumulation of Hexagonal Nanorods for Dye Sensitized Solar Cell (DSSC) Application.

Well-crystalline multipod ZnO architectures made by accumulation of hexagonal nanorods were synthesized, characterized and used as efficient anode material for the fabrication of dye-sensitized solar cell (DSSC). The multipod ZnO architectures were synthesized by simple and facile hydrothermal process and characterized by several techniques to examine the structural, morphological, optical and photovoltaic properties. The morphological characterizations revealed that the synthesized multipod ZnO architectures were made of several hexagonal shaped ZnO nanorods which are originated from a single centre. The structural and compositional properties revealed that the nanorods are pure ZnO and possessing well crystallinity and wurtzite hexagonal phase. The assynthesized multipods ZnO architectures were utilized as potential anode materials for the fabrication of dye-sensitized solar cell (DSSC). The dye sensitized solar cells fabricated with multipods ZnO architectures photoanode attained a reasonable solar to electricity energy conversion efficiency of -1.9% with a photocurrent density i.e., short circuit current (J(sc)) of 4.59 mA/cm2.

One-Pot Synthesis of Multipod ZnO-Carbon Nanotube-Reduced Graphene Oxide Composites with High Performance in Photocatalysis.

Multipod ZnO-multi-walled carbon nanotube (MWCNT)-reduced graphene oxide (RGO) ternary nanocomposites were synthesized via a simple one-pot hydrothermal process using graphene oxide (GO)-dispersed MWCNT and zinc nitrate as raw materials. Scanning electron microscopy analysis indicated the formation of multipod structure of ZnO in the presence of MWCNT. XRD confirmed that the ZnO multipod was in a hexagonal phase while UV-vis and FTIR spectroscopy confirmed that the graphene oxide in the resulting material was in the reduced form. The as-prepared MWCNT-RGO-ZnO composites displayed excellent photocatalytic performance towards the degradation of methylene blue. More specifically, the degradation rate constant of using MWCNT-RGO-ZnO composites were twice and thrice higher than those of using RGO-ZnO composites and bare ZnO material, respectively. The main reason of enhanced photocatalytic property might be due to the internal stepwise energy level of the three components, which helped the electron separation and hinder the charge recombination.

Synthesis of Ag–ZnO with multiple rods (multipods) morphology and its application in the simultaneous photo-catalytic degradation of methyl orange and methylene blue

In this study, the photo-decolorization of a mixture of methylene blue (MB) and methyl orange (MO) was investigated using Ag–ZnO multipods. The photo-catalyst used, ZnO multipods, was successfully synthesized. The surface of ZnO microstructure was modified by deposition of different amounts of Ag nanoparticles (Ag NPs) using the photo-reduction method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis and atomic absorption spectroscopy. The photo-catalytic efficiency of Ag–ZnO is mainly controlled by the amount of Ag NPs deposited on the ZnO surface. The results obtained suggest that Ag–ZnO containing 6.5% Ag NPs, has the highest photo-catalytic performance in the simultaneous photo-degradation of dyes at a shorter time.

Synthesis and application of multiple rods gold–zinc oxide nanostructures in the photocatalytic degradation of methyl orange

Zinc oxide and gold–zinc oxide (Au–ZnO) nanostructures with multiple rods (multipods) morphology were successfully prepared. Au–ZnO nanostructures were synthesized via a simple precipitation route method in the presence of oligoaniline-coated gold nanoparticles. The Au–ZnO catalyst obtained was applied for the degradation of methyl orange in an aqueous solution under UV irradiation. Effects of the operational parameters such as the solution pH, amount of photocatalyst, and dye concentration on the photocatalytic degradation and decolorization of methyl orange were studied. Detailed studies including kinetic study and regeneration of catalyst were carried out on the optimal conditions for the photodegradation of methyl orange by Au–ZnO multipods in aqueous solution. Effect of foreign species on the photodegradation of methyl orange was also studied. An enhancement of the photocatalytic activities for photodegradation of methyl orange was observed when the gold nanoparticles were loaded on the zinc oxide multipods. The proposed catalyst was applied for the degradation of methyl orange in synthetic wastewater samples with satisfactory results.

Structural and optical properties of TZO thin films

In this paper, the synthesis route and growth mechanism of ZnO nanowhiskers and multipods are investigated. A simple chemical deposition route is used to synthesize tin doped zinc oxide (TZO) nanostructures using a horizontal quartz furnace. To study the effect of tin doping on the morphology of ZnO thin film, nanostructures with different morphologies and sizes were grown on silicon wafers and ITO substrates using thermal evaporation of a mixture of zinc, tin, and graphite powders at 1000 °C in a pure oxygen atmosphere. Structural studies of the synthesized ZnO nanostructures were done by means of XRD, SEM, and HRTEM. An XRD graph confirmed the formation of a pure ZnO phase. The SEM and HRTEM images exhibited nanowhiskers with dimensions of an average width of 100 nm and a few micrometers in length. The photoluminescent properties of these structures were also investigated where it shows strong blue-green emission at room temperature for the samples doped with tin.

Shape controlled Sn doped ZnO nanostructures for tunable optical emission and transport properties

Pure and Sn doped ZnO nanostructures have been grown on SiO2/Si substrates by vapor-solid technique without using any catalysts. It has been found that the morphology of the nanostructures depend strongly on the growth temperature and doping concentration. By proper tuning of the growth temperature, morphology of pure ZnO can be changed from tetrapods to multipods. On the other hand, by varying the doping concentration of Sn in ZnO, the morphology can be tuned from tetrapods to flower-like multipods to nanowires. X-ray diffraction pattern reveals that the nanostructures have a preferred (0002) growth orientation, and they are tensile strained with the increase of Sn doping in ZnO. Temperature-dependent photoluminescence characteristics of these nanostructures have been investigated in the range from 10 to 300 K. Pure ZnO tetrapods exhibited less defect state emissions than that of pure ZnO multipods. The defect emission is reduced with low concentration of Sn doping, but again increases at higher concentration of doping because of increased defects. Transport properties of pure and Sn doped ZnO tetrapods have been studied using complex-plane impedance spectroscopy. The contribution from the arms and junctions of a tetrapod could be distinguished. Sn doped ZnO samples showed lower conductivity but higher relaxation time than that of pure ZnO tetrapods.

Growth and characterization of ZnO multipods on functional surfaces with different sizes and shapes of Ag particles

Three-dimensional ZnO multipods are successfully synthesized on functional substrates using the vapor transport method in a quartz tube. The functional surfaces, which include two different distributions of Ag nanoparticles and a layer of commercial Ag nanowires, are coated onto silicon substrates before the growth of ZnO nanostructures. The structures and morphologies of the ZnO/Ag heterostructures are investigated using X-ray diffraction and field emission scanning electron microscopy. The sizes and shapes of the Ag particles affect the growth rates and initial nucleations of the ZnO structures, resulting in different numbers and shapes of multipods. They also influence the orientation and growth quality of the rods. The optical properties are studied by photoluminescence, UV-vis, and Raman spectroscopy. The results indicate that the surface plasmon resonance strongly depends on the sizes and shapes of the Ag particles.

Synthesis and Characterizations of Cd-Doped ZnO Multipods for Environmental Remediation Application

Well-crystalline Cd-doped ZnO multipods were synthesized by simple and facile hydrothermal process by using zinc chloride, cadmium chloride, hexamethylenetetramine and ammonium hydroxide at low-temperature. The synthesized materials were characterized in terms of their morphological, structural, compositional and optical properties. The morphological investigations done by field emission scanning electron microscopy (FESEM) reveal that the synthesized products are multipods shaped and grown in high density. The structural and compositional properties, observed by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) attached with FESEM and Fourier transform infrared (FTIR) spectroscopy exhibit that the synthesized multipods are well-crystalline and possessing wurtzite hexagonal phase pure Cd-doped ZnO. The as-synthesized Cd-doped ZnO multipods exhibited good optical properties as was confirmed by UV-vis. spectroscopy. Finally, the as-synthesized Cd-doped ZnO multipods were used environmental remediation application. For this, the synthesized multipods were used as an effective photocatalyst for the photocatalytic degradation of acridine orange (AO) which exhibit -92.4% degradation within 90 min. This work demonstrates that doped ZnO materials could be used as efficient photocatalyst for the photocatalytic degradation of various organic dyes and chemicals.

Microwave‐Assisted Rapid Synthesis of ZnO Hexagonal Quasi‐Hourglasses

To controllably construct ZnO‐base heterostructures, unique ZnO hexagonal quasi‐hourglasses have been synthesized by a microwave‐assisted hydrothermal approach. The phase purity and the morphologies of as‐prepared samples have been determined by using X‐ray powder diffractometer, field‐emission scanning electron microscopy and transmission electron microscopy. We have rationally discussed the growth and reaction mechanism and revealed the morphological evolution of ZnO hexagonal quasi‐hourglasses. Dodecylamine, as well as the initial concentration of zinc source, the reaction temperature and time, play an important part in the synthesis of ZnO hexagonal quasi‐hourglasses. Between ZnO and Zn5(OH)8(NO3)2, a reversible reaction seldom reported occurs in a circular manner as the reaction proceeds continuously. The presence of ZnO multipods in the products and the controllable synthesis of half of ZnO hexagonal quasi‐hourglass betoken a possibility to synthesize ZnO hierarchical architectures, even ZnO‐base heterostructures by using this kind of ZnO building blocks.

Synthesis, characterization and optical properties of graphene sheets-ZnO multipod nanocomposites

In this paper, attention is focused on the synthesis of graphene sheets-ZnO (GSs-ZnO) multipod nanocomposite. Graphene-based composites are emerging as a new class of materials that hold promise for many curious applications in different areas. In this section, we report a suitable approach for the formation of GSs-ZnO composites through two-step processes. Initially, graphene nanosheets are synthesized by solvothermal method and in the second-stage GSs-ZnO composite is synthesized by hydrothermal method using water as solvent. It was observed that ZnO multipods were randomly dispersed on the surfaces of graphene sheets (GSs). We have also carried out the structural and optical characterizations of GSs-ZnO nanocomposites. The hybridized structure of ZnO and graphene nanosheets has been further investigated by HRTEM. The 2-D graphene nanosheets and ZnO multipod are clearly observed in the TEM microstructures indicating the formation of nanocomposite structure. Raman and FTIR investigations of GSs-ZnO nanocomposite have also shown the signature of nanocomposite formation. In addition, a photoluminescence spectrum of GSs-ZnO multipod nanocomposites displays the fluorescence quenching property.

Fabrication and characterisation of multipod ZnO nanostructures by CVD on Al 2 O 3 -coat Si (111) substrate

Multipod ZnO nanostructures were fabricated on Al2O3-coat Si (111) substrate by chemical vapour deposition method at 1050°C using the mixture of ZnO and C powders as source materials. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy were used to synthesise the structure, morphology and microstructure of the multipod ZnO nanostructures. X-ray photoelectron spectroscopy was used to investigate the chemical composition of the multipod ZnO nanostructure. Finally, the growth mechanism of the multipod ZnO nanostructures was also discussed.

Synthesis of porous and nonporous ZnO nanobelt, multipod, and hierarchical nanostructure from Zn-HDS

Zn based hydroxide double salts (Zn-HDS) with an interlayer spacing of 20 Å was produced by dissolving dumbbell-like ZnO crystal. The resulting Zn-HDS with a ribbon-like shape has a suitable morphology to explore the remarkably mild procedure for synthesis of ZnO nanobelts. We found that the intercalated water molecules into the Zn-HDS could play a key role in the ZnO nanobelts porosity. The nonporous ZnO nanobelts were successfully synthesized from the Zn-HDS by soft-solution process at 95 °C through mild dehydration agent as Na 2CO 3. As-synthesized ZnO nanobelts were grown along not only the [0 1 −1 0], but also the [2 −1 −1 0]. On the other hand, the porous ZnO nanobelts were obtained from the Zn-HDS by calcinations at 200 and 400 °C. In addition, flower-like ZnO multipod and hierarchical nanostructures were produced from the Zn-HDS by using of strong dehydration agent (NaOH) through hydrothermal reaction at 150 and 230 °C.

Photoluminescence and Raman analysis of novel ZnO tetrapod and multipod nanostructures

Novel ZnO tetrapod and multipod nanostructures were successfully synthesized in bulk quantity through thermal evaporation method. The morphologies and structures of the ZnO nanostructures were characterized by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The results revealed that the ZnO nanostructures consisted of tetrapods and multipods with tower-like legs. The ZnO nanostructures were of high purity and were well crystallized with wurtzite structure. The preferred growth direction of legs was found to be the [0 0 0 1] direction. Possible growth mechanisms were proposed for the formation of the ZnO nanostructures. Room temperature photoluminescence (PL) spectra showed that the as-synthesized ZnO nanostructures had a strong green emission centered at 495 nm and a weak ultraviolet emission at 383 nm. Raman spectroscopy was also adopted to explore the structural quality of the ZnO nanostructures.